1863.] DAT LIAS OF DOKSETSHIRE. 287 



In the first cliff east of the harbour, there is a thickness of about 

 120 or 130 feet of sands with nodules, cut into a perpendicular cliff. 

 Probably some of the highest nodules of the sands cap this cliff, as I 

 have seen a few fossils in blocks fallen from the summit, and as the 

 Inferior Oolite is found a very short distance inland. 



6. Burton Cliff. — In this section there is the same thickness of 

 sands as in the last-mentioned cliff, but here capped by the Inferior 

 Oolite and Fuller's Earth. As much discussion has taken place in 

 England upon the correctness of the classification which assigns 

 these sands to the Upper Lias, and as I believe some amount of 

 doubt was at one time expressed, not only upon the deductions 

 drawn from the assertions made upon this point, but even upon 

 those assertions themselves, I am happy to be able to add my testi- 

 mony to the truth of one point which was formerly called in ques- 

 tion, namely, the existence of a bed containing numerous Ammo- 

 nites, of species assigned on the Continent to the Upper Lias, lying 

 in the sands a few feet under the lowest beds of the Inferior Oolite. 

 From the geologist who first pointed out this Ammonite-bed, it is 

 frequently called the Cephalopoda-bed of Dr. Wright * ; and I have 

 now found it in this district, not only in Burton Cliff, but under- 

 lying the Inferior Oolite of Chideock Hill, of Poorstock, and of Stoke 

 Knap, near Broad Windsor. 



Only the highest nodules of the sands are fossiliferous, and the 

 uppermost tier of all is a persistent bed of sandstone, containing 

 much lime and densely charged with the casts of Ammonites and 

 other shells. Under Burton Cliff, on the occasion of a visit thither 

 in the company of my friends Dr. Wright f and Robert Etheridge, 

 Esq., we found the bed of stone here mentioned still attached to the 

 base of the limestone containing Ammonites Humphriesianus, Sow. ; 

 the zone of A. Murchisonce, Sow., being here absent. In the other 

 localities above given, I have found the same bed underlying the 

 zone last mentioned, the absence of which, in Burton Cliff, appears 

 to be the exception in this district. 



7. Generalized Section. — With the last section ends my description 

 of the lithological characters of the Middle and Upper Lias of this 

 coast, which divisions I have thus traced, from the first appearance 

 of the lower, in the cliffs of Black Yen, to the point of disappearance 

 of the upper, near the village of Burton-Bradstock. 



I now propose to condense these several sections into one gene- 

 ralized diagram, in which I shall endeavour to point out how the 

 fossils are distributed through the successive beds of varying litho- 

 logical character. 



Commencing from below, there is first a great mass of marls con- 

 taining more or less persistent beds of limestones, or limestone- 

 nodules, but all without a trace of mica. This mass, nearly 200 

 feet in thickness, as seen inWesthay Cliffs, is terminated by a de- 

 posit of lime, sand, and mica, forming the " Three Tiers." Over this 



* See Quart. Journ. Geol. Soc. vol. xii. p. 292, and vol. xvi. p. 3. 



t I have to thank Dr. Wright, with whom I first visited some of the sections 

 described, for his kindness in determining many specimens, which I submitted 

 to him, illustrative of these strata. 



